Severe Thunderstorm Warning 275, NWS Raleigh, NC

Area Forecast Discussion
National Weather Service Raleigh NC
832 PM EDT TUE SEP 27 2016

.SYNOPSIS...
A quasi-stationary frontal zone will meander over the area
through late in the work week, as a deep upper level low settles
over the Tennessee Valley.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 845 PM Tuesday

While the threat for isolated strong/severe storms has decreased
with loss of heating, scattered showers and thunderstorms with
locally heavy downpours will remain a decent probability across
roughly the west half of central NC through midnight, with coverage
expected to gradually decrease afterwards.

A very moist air mass for this time of year (PW values 120-150
percent of normal) coupled with lift supplied by an upper jet
crossing the northern mid atlantic and weak low level convergence
along a slow moving cold front will maintain the threat for
scattered showers/storms through the rest of the evening. this
forcing is maximized west of highway 1 through 06Z, then projected
to weaken through 12Z Wednesday. Will need to monitor for training
showers/storms as high PW values indicate the atmosphere supportive
if efficient rain producing storms, which may lead to localized
flood threat.

Across the coastal plain, forcing not as robust though atmosphere
just as moist. While showers/storms will not be as numerous compared
to the Piedmont, locally heavy rainfall will still occur with the
stronger showers/storms.

Overnight temps in the 65-70 degree range expected.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 330 PM Tuesday...

Depending on the amount of ongoing showers early wednesday
morning, Wednesday afternoon could be a rather active. As the
stacked low over the Great Lakes digs south toward the TN Valley,
increased forcing for accent and the stalled frontal zone over
west-central NC will trigger convection, though the timing of
greatest coverage is still a little uncertain given that the best
height falls and cooling aloft won't arrive until later Wednesday
afternoon/evening, possibly toward the end of peak heating. Deep
shear, while strongest to the northwest, will increase to 30-40kt,
especially as the low-level flow backs in response to the
approaching height falls, which may support supercell activity
within a band of convection that appears favored from US-1 east,
based on the available CAMs. All of central NC is in a Marginal
Risk (per SPC) and this could be upgraded if instability appears
to be sufficiently strong.

The other concern for Wednesday evening is isolated flash
flooding given system parallel southwesterly mean flow and PW
near 2 inches. At the moment, Flash Flood Guidance for 3+ hours is
well in excess of 2 inches. The GEFS and EC Ensemble means are
roughly 1-2 inches for the central and northern Piedmont areas,
so urban areas would likely run the greatest risk. However,
confidence in the most favored area is not high enough to consider
a watch at this time.

Even after an evening round of convection "occurs" the ECMWF
indicates another round of precip overnight, which isn't out of
the question given cyclonic flow aloft and no airmass change. it's
hard to put much detail into that portion of the forecast until
the mesoscale aspects of Wednesday evening play out, but POPs
will remain high overnight.

Highs Wednesday should be in the mid 70s to lower 80s, with
overnight lows in the mid and upper 70s.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 355 PM Tuesday...

A closed mid-upper low now over the Great Lakes will settle SWD and
become increasingly separated/cut-off from the NRN stream flow
across Canada, and ultimately reach the Lower OH/NRN TN Valley by
early Thu. The models agree that the low will linger there through
Fri, then lift NNEWD across the Great Lakes through the weekend.
Meanwhile, a SRN stream jet will help carve a lingering trough axis
across the SERN U.S. and ERN GOM, SWD to the vicinity of the
Yucatan, during the same time. The ultimate placement and strength
of this latter feature may play a role in the eventual track and
strength of the tropical wave now several hundred miles E of
Barbados.

At the surface, a secondary cold front associated with the
aforementioned closed low will have moved into the Appalachians by
early Thu, then drift slowly EWD and merge, over central NC Thu
afternoon, with the preceding frontal zone now stretching along the
NC Blue Ridge. The front, and large-scale forcing and ERN fringe of
colder temperatures/steep lapse rates accompanying the mid-upper
low, will serve as a continued focus for a good chance of showers
and storms on Thu. The merged frontal zone --and associated WRN
bound of instability/convergence/chance of showers and storms-- will
then pivot slowly NEWD through the NE Piedmont and Coastal Plain Thu
night-Fri, before reaching and dissipating along the coast late Fri-
Sat.

A lee trough and associated light SLY flow will linger over the
Carolinas this weekend, then yield to high pressure forecast to
build across the NERN quarter of the CONUS, beneath NRN stream
ridging aloft, through early-mid next week.

Temperatures are expected to be near to slightly above average
throughout the period.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 831 PM Tuesday...

Scattered showers and storms will become less numerous over the next
several hours. With a moist low level air mass, IFR stratus looks
likely at KINT/KGSO, while sub-VFR conditions with some patchy fog
are possible elsewhere in the early morning hours. Stationary front
will remain west of the area Wednesday, and showers and
thunderstorms will develop again across the area Wednesday
afternoon.

Looking beyond the 24 TAF Period:  The combination of a quasi-
stationary front across the Carolinas and a cut-off upper level low
settling over the Tennessee Valley will keep unsettled weather in the
form of scattered to numerous showers and storms through Thursday.
Conditions are expected to improve Friday through the weekend as
drier air finally spreads in from the west.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

SYNOPSIS...SMITH
NEAR TERM...WSS
SHORT TERM...SMITH
LONG TERM...MWS
AVIATION...30/SMITH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RALEIGH NC
401 PM EDT TUE SEP 27 2016

NCZ007>011-021>028-038>043-073>078-083>086-088-089-282015-
PERSON-GRANVILLE-VANCE-WARREN-HALIFAX-FORSYTH-GUILFORD-ALAMANCE-
ORANGE-DURHAM-FRANKLIN-NASH-EDGECOMBE-DAVIDSON-RANDOLPH-CHATHAM-WAKE-
JOHNSTON-WILSON-STANLY-MONTGOMERY-MOORE-LEE-HARNETT-WAYNE-ANSON-
RICHMOND-SCOTLAND-HOKE-CUMBERLAND-SAMPSON-
401 PM EDT TUE SEP 27 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL NORTH CAROLINA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

AN ISOLATED STORM OR TWO COULD PRODUCE SMALL HAIL AND WIND GUSTS
UP TO 50 MPH THIS EVENING.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

A DEEP UPPER LOW SETTLING OVER THE TENNESSEE VALLEY AND A STALLED
FRONT OVER NC WILL LEAD TO NUMEROUS SHOWERS AND STORMS WEDNESDAY
AFTERNOON INTO WEDNESDAY NIGHT, SOME OF WHICH MAY BE SEVERE WITH
DAMAGING WINDS. MULTIPLE ROUNDS OF HEAVY RAIN MAY ALSO LEAD TO
LOCALIZED FLOODING, ESPECIALLY IN URBAN AND POOR DRAINAGE AREAS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEED WEDNESDAY EVENING.

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RALEIGH NC
341 PM EDT TUE SEP 27 2016

NCZ089-272030-
SAMPSON  NC-
341 PM EDT TUE SEP 27 2016

 ...A STRONG THUNDERSTORM WILL AFFECT PORTIONS OF NORTHERN SAMPSON
COUNTY UNTIL 430 PM EDT...

AT 341 PM EDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM 9
MILES SOUTHEAST OF GODWIN...OR 16 MILES NORTHWEST OF CLINTON...MOVING
EAST AT 20 MPH.

PEA SIZE HAIL AND WIND GUSTS UP TO 40 MPH WILL BE POSSIBLE WITH THIS
STORM.

HEAVY RAIN AND MINOR FLOODING WILL ALSO BE POSSIBLE WITH THIS STORM.

LOCATIONS IMPACTED INCLUDE...
CLINTON...SALEMBURG AND TURKEY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

LOCALLY HEAVY RAIN WILL QUICKLY REDUCE VISIBILITY AND RESULT IN
PONDING OF WATER ON ROADWAYS...STANDING WATER IN LOW LYING
AREAS...AND MINOR FLOODING OF CREEKS...STREAMS...AND AREAS OF POOR
DRAINAGE. DRIVERS ARE URGED TO SLOW DOWN AND USE EXTRA CAUTION TO
AVOID HYDROPLANING...ESPECIALLY IN URBAN AREAS WHERE PROLONGED HEAVY
RAIN CAN QUICKLY LEAD TO FLOODING.

&&

LAT...LON 3502 7865 3509 7867 3512 7864 3512 7865
      3514 7864 3517 7864 3517 7863 3520 7864
      3521 7863 3521 7860 3513 7817 3509 7817
      3508 7816 3501 7815 3487 7821
TIME...MOT...LOC 1941Z 287DEG 16KT 3511 7859

WSS

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RALEIGH NC
749 PM EDT TUE SEP 27 2016

NCZ038-039-073-074-280030-
RANDOLPH  NC-DAVIDSON  NC-STANLY  NC-MONTGOMERY  NC-
749 PM EDT TUE SEP 27 2016

 ...A STRONG THUNDERSTORM WILL AFFECT PORTIONS OF SOUTHWESTERN
RANDOLPH...SOUTHEASTERN DAVIDSON...NORTHEASTERN STANLY AND
NORTHWESTERN MONTGOMERY COUNTIES UNTIL 830 PM EDT...

AT 749 PM EDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM OVER
BADIN LAKE...MOVING NORTHEAST AT 20 MPH.

PEA SIZE HAIL AND WIND GUSTS UP TO 40 MPH WILL BE POSSIBLE WITH THIS
STORM.

HEAVY RAIN AND MINOR FLOODING WILL ALSO BE POSSIBLE WITH THIS STORM.

LOCATIONS IMPACTED INCLUDE...
ASHEBORO...BADIN LAKE...NORTH CAROLINA ZOO...SEAGROVE...BADIN...NEW
LONDON...FISH TALES MARINA...ULAH...MARTHA AND MORROW MOUNTAIN STATE
PARK.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

LOCALLY HEAVY RAIN WILL QUICKLY REDUCE VISIBILITY AND RESULT IN
PONDING OF WATER ON ROADWAYS...STANDING WATER IN LOW LYING
AREAS...AND MINOR FLOODING OF CREEKS...STREAMS...AND AREAS OF POOR
DRAINAGE. DRIVERS ARE URGED TO SLOW DOWN AND USE EXTRA CAUTION TO
AVOID HYDROPLANING...ESPECIALLY IN URBAN AREAS WHERE PROLONGED HEAVY
RAIN CAN QUICKLY LEAD TO FLOODING.

&&

LAT...LON 3578 7983 3557 7963 3551 7975 3551 7977
      3550 7977 3533 8011 3547 8024
TIME...MOT...LOC 2349Z 232DEG 17KT 3545 8011

WSS

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RALEIGH NC
841 PM EDT TUE SEP 27 2016

NCZ039-040-074-075-280130-
RANDOLPH  NC-CHATHAM  NC-MOORE  NC-MONTGOMERY  NC-
841 PM EDT TUE SEP 27 2016

 ...A STRONG THUNDERSTORM WILL AFFECT PORTIONS OF SOUTHEASTERN
RANDOLPH...SOUTHWESTERN CHATHAM...NORTHWESTERN MOORE AND NORTHERN
MONTGOMERY COUNTIES UNTIL 930 PM EDT...

AT 840 PM EDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM NEAR
TROY...MOVING NORTHEAST AT 30 MPH.

PEA SIZE HAIL AND WIND GUSTS UP TO 40 MPH WILL BE POSSIBLE WITH THIS
STORM.

HEAVY RAIN AND MINOR FLOODING WILL ALSO BE POSSIBLE WITH THIS STORM.

LOCATIONS IMPACTED INCLUDE...
TROY...NORTH CAROLINA ZOO...BISCOE...SEAGROVE...ROBBINS...STAR...
HARPERS CROSSROADS...STEEDS...HIGHFALLS AND COLERIDGE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

SEEK SHELTER IN A NEARBY BUILDING OR VEHICLE. WIND GUSTS AS HIGH AS
40 MPH ARE CAPABLE OF KNOCKING DOWN TREE LIMBS AND BLOWING AROUND
TRASH CANS...AND OTHER LIGHT OUTDOOR OBJECTS.

&&

LAT...LON 3577 7957 3555 7936 3524 7995 3536 8006
      3537 8005 3539 8007
TIME...MOT...LOC 0040Z 231DEG 24KT 3536 7995

WSS